1. Field of the Invention
The present invention relates to an electrostatic chuck for electrostatically attracting and securely holding an object such as a semiconductor wafer.
2. Description of the Relevant Art
Recent years have seen the use of an electrostatic chuck as a jig for firmly holding a semiconductor wafer while the semiconductor wafer is being processed at very small dimensions, e.g., while it is being patterned.
For example, Japanese Patent Publication No. 60(1985)-59104 discloses an electrostatic chuck including an electrode plate having one surface on which an electrically insulating dielectric layer of alumina or the like is deposited by flame spraying. An object such as a semiconductor wafer is placed on the dielectric layer, and a voltage is applied across the dielectric layer between the wafer and the electrode plate for holding the wafer on the dielectric layer.
With the conventional electrostatic chuck, the dielectric layer has a large volume resistivity .rho. of about 10.sup.1 4 .OMEGA..multidot.cm, and almost no electric charges move in the dielectric layer. The wafer is attracted by an electrostatic force developed between the electrode plate to which the voltage is applied and the object itself. However, the electrostatic force thus produced is small and does not sufficiently attract the object.